The objective of this research is to provide an understanding of the structural and functional features of the polyoma virus origin region and those gene products which enable the virus to replicate its DNA, transcribe RNA's and transform cells in culture. Existing deletion and insertion mutants, together with newly isolated point mutants will be used to characterize the regulation of RNA transcription, splicing and DNA replication. These processes will be correlated with the physical structure of this region (organized into nucleosomes). T-antigens of polyoma virus will be purified from bacterial and/or animal cells containing modified viral genomes which permit high efficiency expression. The capacity of these purified proteins to interact with the modified viral origin region will be explored.